1. Field of the Invention
The invention relates to a magnetic head with layered structure for magnetizing a recording medium perpendicularly in a manner that is often referred to as vertical magnetization. A magnetic head with a structure for producing such magnetization is disclosed in West Germany Pat. No. 2,924,013 or U.S. Pat. No. 4,287,544. The invention also relates to a method for the production of magnetic heads.
2. Description of Related Knowledge
The concept of perpendicular magnetization of a suitable recording media for data storage is generally known (cf. "IEEE Transactions on Magnetics", Vol. MAG-16, No. 1, Jan. 1980, pp. 71 to 76 or Vol. MAG-20, No. 5, Sept. 1984, pp. 657 to 662 and 675 to 680). Application of this concept, which is also called vertical magnetization, requires specific read/write magnetic heads and particular recording media. A head suitable for this application generally uses a conductor body made of a magnetizable material to conduct the magnetic flux and shaped to have two magnet legs in the shape of a horseshoe. One magnetic leg forms a main pole and generates a sufficiently strong perpendicular magnetic field to magnetically reverse the storage layer of the recording medium along a track. The other magnet leg returns the magnetic flux through a second pole which is termed an auxiliary pole.
In magnetic heads of this head type the auxiliary pole serves solely for guiding the magnetic return flux. This head type writes solely with the main pole and is therefore also called a single pole-piece head.
West German Pat. No. 2,924,013 describes a head of this type (cf. "IEEE Trans. Magn.", Vol. MAG-17, No. 6, Nov. 1981, pp. 3120 to 3122). Accordingly, the known magnetic head contains the auxiliary pole at its front end when viewed along the line of travel of the recording medium. The main pole is located on the back face. The two poles are arranged on a flat surface of a non-magnetic substrate with the normal on this surface being parallel to the direction of travel. The main pole consists essentially of a thin layer extending perpendicularly to the line of travel of the end piece of the corresponding magnet leg. In contrast, the auxiliary pole lies in front of the main pole in its line of travel. The auxiliary pole is formed from an end piece and is significantly thicker than that of the other magnet leg. This auxiliary pole is composed of several thin magnetic layers arranged perpendicularly to the line of travel. Each layer is separated by an insulating layer. Several steps must be taken to prevent co-reading of the auxiliary pole. Its flow-off edge covers a comparatively large area of the track. The distance formed between the two poles must be sufficiently great to ensure an extensive reduction in the magnetic flux density at the auxiliary pole. Therefore, an air gap between the two poles of at least 5 .mu.m in width is generally provided.
Any remaining space of the air gap that faces the recording media of this known magnetic head that is not taken up by the conductor windings of a read/write wire-wound coil must be filled with, at least, an insulating gap layer. A suitable insulating layer should consist of a hard material so that notches and washouts can be prevented in the process of producing the head. It is known that accumulated dust can cause uneven sites to occur on the disk by causing the magnetic head to crash as it guides over the recording medium at an extremely close distance. It is known to be extremely difficult to cause a known magnetic head to create its own gap layer between the main pole and the auxiliary pole. Problems arise in creating a magnetic flux return in the back part of the magnetic head between the two magnet legs where the gap layer must be etched through. The known magnetic head has a relatively extended structure when seen in the line of travel. Moreover, smoothing is problematic so that the magnetic properties of the main pole can be impaired due to the relatively extended structure of the known magnetic head.
Great Britain Pat. No. 2,058,436 discloses a magnetic head that has a shape resembling a ring with one of two magnet legs located in a depression of a substrate. However, the end pieces of the magnet legs forming the magnetic poles are so closely adjacent to each other that the head cannot have a main and auxiliary pole and therefore cannot function as a single pole-piece head. This type head does, however, eliminate problems associated with developing a broad gap layer. Furthermore, in this known magnetic head the portion of the one magnet leg submerged in the substrate does not lie in the region of the magnetic pole but in a central expanded head region through which the conductor windings of the read/write wire-wound coils extend. A similar structure of a magnetic head with closely adjacent magnetic poles is disclosed in European Patent Application No. 185,289.